1. Field of the Invention
The present invention relates in general to the field of catheters for use in exploratory procedures, diagnosis and treatment of biologic conditions, and more particularly, to a catheter meter for determining spacial quantities such as linear distance in a vessel or other comparable environment.
2. Related Art
Catheters are well known in the art and are commonly introduced or inserted into canals, vessels, passageways or body cavities to inspect a region of interest or inject or withdraw fluids from the region or to treat the region, such as to keep a restricted passage open. One medical procedure is known as angioplasty, which has become widely accepted as a safe and effective method for treating various types of vascular diseases. For example, angioplasty has been used for opening stenoses throughout the vascular system, and particularly for opening stenoses in coronary arteries. One common form of angioplasty is called percutaneous transluminal coronary angioplasty. This procedure uses a dilation catheter having an inflatable balloon at is distal end. Using a fluoroscope and radiopaque dyes for visualization, the distal end of the dilation catheter is guided into position across the stenosis and the balloon is inflated for a brief period to reopen the artery and reestablish adequate blood flow.
A number of balloon catheter designs have been developed and have contributed to the safety and acceptability of percutaneous transluminal coronary angioplasty and similar medical procedures. The most common design is known as an "over the wire" balloon catheter. This prior art device typically uses a relatively large lumen for passing a guide wire and injecting angiographic visualization dye to assist in placing the device. A second parallel lumen is provided for inflation and deflation of the balloon. Typically, a steerable guide wire is positioned within the larger lumen and the entire assembly is maneuvered into an initial position within the target artery through a previously positioned large diameter guide catheter. Once near the sight of the stenosis, the guide wire can be rotated and axially extended or retracted into position across the lesion. The catheter is then advanced along the guide wire to position its balloon end across the lesion prior to inflation of the balloon and dilation of the stenosis.
Typically, the vascular stenosis is located and the dilation balloon positioned by fluoroscopy. In that procedure, the radiopaque dyes are injected into the vessel after the catheter has been introduced into the vessel. The stenosis is then located and the end of the catheter is determined relative to the stenosis. The inflatable balloon can then be moved across the stenosis and inflated to open the stenosis. While fluoroscopy is a well accepted procedure and can be properly carried out by an experienced physician, it nonetheless requires injection of the radiopaque dyes and use of x-rays to be able to view the remote area of interest.
Once the stenosis is located, dilating the stenotic lesion requires a substantial effort, which is not always entirely successful. For example, successful treatment requires a properly sized inflation balloon to be placed across the stenosis and inflated to remove the stenosis. Determining the proper balloon size is often difficult and not always correct on the first try, requiring a second procedure with a different sized balloon.
In one procedure for estimating the size of the stenotic lesion, sufficient radiopaque dye must be kept in the vessel to permit viewing by fluoroscope. In order to obtain sufficient information about the stenotic lesion to estimate its size, the patient must be turned through various positions to obtain a series of different views of the vessel. If the patient remains sufficiently immobile, sufficient views of the vessel taken, even though the vessel such as a cardiac artery may be moving, and the radiopaque dye is maintained in the vessel, it is nonetheless difficult to accurately estimate the size and form of the stenotic lesion.
If the inflatable balloon chosen to open the stenotic lesion is too small, the stenosis will not be sufficiently opened, and a larger balloon must be used after the first procedure. If the inflatable balloon is too larger, the vessel may reflexively reconstrict, limiting adequate blood flow through the vessel. Repeated processes result in trauma to the patient and possible harm to the vessel receiving the catheter, thereby increasing the risk of complications. Therefore, it is not only difficult to accurately measure linear distances using catheters but it is also difficult to adequately measure other quantifiable parameter such as size and shape. This inability to adequately measure and quantify unknown quantities and the possibility of repeated procedures may ultimately lead to complications during certain medical procedures.
In the past these duel lumen catheters, however, have been relatively bulky and stiff, making their use difficult for any lesions except those proximal and localized in non-tortuous, easily accessible vessels.
Accordingly, it is an object of the present invention to provide a catheter depth gauge which can measure linear distance from the top or proximal of the catheter device to an object of interest at the distal end.
It is an additional object of the present invention to provide a device which will allow a physician to quantify distances and other spacial parameters in order to provide a reference point for surgery, data for diagnosis and treatment of symptoms and to minimize the number of procedures and steps necessary to achieve the desired result.
It is a further object of the present invention to provide a device which allows a physician to determine the size and extent of conditions such as vascular stenosis for purposes of diagnosis and treatment of vascular disease.
It is an additional object of the present invention to provide a device which allows a physician to determine which vascular areas of a particular vessel should be treated and which areas may be passed over. These and other objects are achieved by the device of the present invention.